1. Field of the Invention
The present invention relates generally to a medical drill or drill bit, and more particularly to a variable depth medical drill or drill bit having particular applicability as a dental implant drill with improved means for indicating drill depth. The invention also relates to a method of making the above medical drill bit.
2. Description of the Prior Art
In the medical field generally, and in the dental field specifically, drills or drill bits are provided for drilling holes of a specific size and depth in body tissue such as bone or a tooth to a specified depth. For example, a preliminary step in the installation or placement of a dental implant involves drilling a hole in the tooth or tooth root to a specified depth. A dental implant can then be installed into the hole. Accuracy in the depth of the hole is important for a dental implant. If the hole is too shallow, the implant or implant with cover screw will extend above the bone, while if the hole is too deep, the implant will sit below the bone or a pocket will exist at the bottom of the implant. More importantly, inaccurate drill depth can damage vital structures such as nerves and blood vessels. In addition, ultimate success of the implant can be jeopardized. Because of this various drills and techniques have been developed to assist the dentist or other operator in determining the depth of the hole being drilled.
One available drill is a twist drill with spiral flutes extending up the entire length of the drill portion for drawing bone chips and other debris away from the drill tip. Such drills are provided with a plurality of relatively narrow depth indicating rings. These rings are formed by laser etching and are generally black or gray. By drilling a hole to a selected ring, the dentist is able to determine the depth of the hole being drilled. One limitation of this particular drill is the absence of contrast between the laser-etched ring, which is generally black or gray, and the silver color of the stainless steel drill. A second limitation is the absence of any differentiation between the plurality of rings. Thus, it is necessary for the dentist to count the rings as he or she is drilling so that the correct depth is achieved. In some instances, it may be necessary for the dentist to withdraw the drill to recount the rings to make sure that the proper depth of hole is drilled. A third limitation is that the lines tend to wear off with use.
Another drill currently available for use in drilling holes for dental implants is a conventional spade drill having a vertical flute extending up the length of the drill for removing bone and other debris from the cutting tip. Such drill includes a plurality of spaced grooves along the body of the drill to indicate the depths of the hole being drilled. This drill suffers from many of the same limitations as the twist drill described above. First, the grooves in the exterior surface of the drill are often difficult to see because they are the same color as the remainder of the drill. This is particularly true inside the mouth during operation when bone and other debris are being removed. Secondly, there is no differentiation between the plurality of grooves or between adjacent grooves, thus, it is difficult for the dentist to determine the depth of the hole without counting and keeping track of the number of grooves or rings during the drilling process. Thus, similar to the twist drill described above, it is often necessary for the dentist to withdraw the drill from the hole during the drilling process to recheck the particular ring which defines the desired depth.
A further drill structure comprises a twist drill with spirally extending flutes and a plurality of wider laser etched bands to improve their visibility. The width of these bands is such that the bottom edge of the band indicates a first depth, while the top edge indicates a second depth. Although this structure attempts to address the problem of depth marking visibility by making the bands wider, and thus more visible, the bands are still in the same color family as the stainless steel drill tend to wear off with use and also do not differentiate between different depth markings.
Accordingly, there is a need in the art for an improved medical drill, and particularly a dental implant drill, which provides an improved means for indicating the particular depth of the drilled hole and for clearly distinguishing between the markings for holes of different depths.